Patent Document 1 discloses the window shade device including two winding shafts arranged relative to one another at arbitrary angles.
As to the window shade device disclosed in Patent Document 1, two configurations in which one winding shaft is rotated in association with the rotation of the other winding shaft are disclosed.
In the first configuration, a threaded spindle is connected to the one winding shaft, and a spindle nut is screwed with this threaded spindle. Then, the winding shaft is rotated for opening/closing one sheet, the spindle nut screwed with the threaded spindle moves along the axial direction of the threaded spindle, so that the other sheet is opened/closed.
In the second configuration, the one winding shaft and the other winding shaft are coupled to each other to rotate in synchronism via a bevel gear wheel. The leading edge of the sheet wound around the other winding shaft is biased in a drawing direction by a tension spring. Then, when the one winding shaft rotates in the direction in which the one sheet is drawn, the other winding shaft rotates in synchronism in the direction in which the sheet is drawn. Accordingly, the sheet wound around the other winding shaft is drawn by a tensile force of the tension spring. Meanwhile, when the one winding shaft rotates in the direction in which the other sheet is wound up, the other winding shaft rotates in synchronism to wind up the sheet.